Patent GB-312638-A (GB)
Title: Improvements relating to automatic synchronizing apparatus for alternating current circuits
IPC: H02J3/42
Filed: 1929-05-09
Abstract: 312,638. Associated Electrical Industries, Ltd., (Assignees of Gulliksen, F. H., and Nycum, H. C.). May 29, 1928, [Convention date]. Synchronizing dynamo-electric machines. - In automatic synchronizing systems, the control circuit of the switch interconnecting two circuits is closed when the difference between the frequencies of the two circuits is below a predetermined value and at a time in advance of phase coincidence varying directly with this difference, i.e. with the beat frequency. The closure of the control circuit may also depend on voltage differences between the circuits and may occur earlier if the voltage of one circuit is low. A series of relays operated successively at intervals depending on the beat frequency prevent closure of the control circuit until one or more cycles of the beat frequency have elapsed after the first phase coincidence at a beat frequency below the predetermined value, but the series of relays may be ineffective if the beat frequency is low. Solenoids 22, 23 connected between the circuits 37, 38 rock pivoted levers 11, 12 with damping dash-pots 44, 45 at a frequency equal to, and with an amplitude inversely proportional to, the beat frequency. Springs 19, 20 are arranged to give a straight line law between the movement of the levers 11, 12 and the spring force acting on them. A spring-controlled pivoted lever 10 is connected to the lever 12 by a dash-pot 24 and carries adjustable contacts 25, 26 co-operating respectively with an adjustable, contact 27 on the lever 11 and a fixed but adjustable contact 28. The contact 25 is lowered by the dash-pot connection 24 by an amount depending on the speed of movement of the lever 12, i.e. on the beat frequency, the contacts 25, 27 meeting at a time in advance of phase coincidence due to this lowering. A needle-valve on a dash-pot 24 may be adjusted to adjust this lowering and so to ensure that the interconnecting switch 41 operates at phase-coincidence. The contacts 25, 27 are in the control circuit of a switch 51 control ling the switch 41, but the switch 51 is energized only when one of switches 50, 52 are closed. Contacts 29, 31, 30 are closed in this order at intervals of half cycles of the beat frequency and energize relays 47, 49, 50 with locking circuits, so that the relay 51 is energized through the contacts of the relay 50 at the next contact between 25, 27. These relays prevent premature closure of the switch 41 due to touching of the contacts 25, 27 when the whole device is de-energized. If the beat frequency is low or zero, a relay 52 with time-delay 53 and energized through contacts 32 closes the circuit instead of the relay 50. When the beat frequency is high, contacts 26, 28 close before the contacts 25, 27 and short-circuit the coils of the relays to prevent operation of the synchronizer. When the circuits 27, 38 are parts of the same system with the same frequency, opposed windings 54 fed through copper-oxide rectifiers 55, 56 from the circuits 37, 38 exert on the lever 11 a torque dependent on the voltage difference between the circuits 37, 38 and so counteract the tendency of the solenoid 22 to prevent contact at 25, 27. The relays 47, 49, 50 may be omitted in this case. When the circuits 37, 38 are at different frequencies, for example, in connecting a generator to a supply circuit, opposed windings 54<1> fed similarly to the windings 54 depress the contact 25 and cause earlier closure of the contacts 25, 27 due to a voltage difference between the circuits 37, 38.